Inkjet printers employing Memjet® technology are commercially available for a number of different printing formats, including small-office-home-office (“SOHO”) printers, label printers and wideformat printers. Memjet® printers typically comprise one or more stationary inkjet printheads, which are user-replaceable. For example, a SOHO printer comprises a single user-replaceable multi-colored printhead, a high-speed label printer comprises a plurality of user-replaceable monochrome printheads aligned along a media feed direction, and a wideformat printer comprises a plurality of user-replaceable multi-colored printheads in a staggered overlapping arrangement so as to span across a wideformat pagewidth.
Providing users with the ability to replace printheads is a key advantage of the Memjet® technology. However, this places demands on the ink delivery system supplying ink to the printhead(s). For example, the ink delivery system should allow expired printheads to be de-primed before replacement so as not to cause inadvertent ink spillages and allow new printheads to be primed with ink after installation.
A number of approaches towards ink delivery systems for inkjet printheads have been described in US2011/0025762; US2011/0279566; and US2011/0279562 (all assigned to the present Applicant), the contents of which are incorporated herein by reference.
The ink delivery systems described previously in connection with Memjet® printers generally comprise a closed loop system having first and second ink conduits interconnecting an ink container with respective first and second ink ports of the printhead. A reversible pump is positioned in the second ink conduit for pumping ink around the closed loop. Typically, a pinch valve is positioned on the first ink conduit for controlling the flow of ink or air through the printhead. As described in US2011/0279566 and US2011/0279562, the pump and pinch valve are coordinated to provide a multitude of printhead priming, de-priming and other maintenance or recovery operations.
It would be desirable to modify the ink delivery systems described in US2011/0279566 and US2011/0279562 so as to improve so-called ‘pulse priming’ or ‘pressure priming’ operations in which ink is forced from all nozzles in the printhead under a positive pressure.